WO2023222859A1

WO2023222859A1 - Injection device

Info

Publication number: WO2023222859A1
Application number: PCT/EP2023/063443
Authority: WO
Inventors: Kevin Stamp
Original assignee: Future Injection Technologies Limited
Priority date: 2022-05-18
Filing date: 2023-05-18
Publication date: 2023-11-23
Also published as: GB202207290D0

Abstract

The invention generally relates to an automatic injection device. The device comprises a syringe having a needle, a barrel and a plunger, as well as driving means for driving the plunger into the barrel. The device may comprise a cap (e.g., rigid needle shield) configured to cover and protect the needle of the syringe prior to use. The injection device is arranged to perform an automatic injection cycle in use comprising the stages of advancing the needle of the syringe for insertion (the "needle advancement stage"), and driving the plunger into the barrel for dispensing a liquid contained in the barrel (the "dispensing stage"). The automatic injection cycle may be activated (e.g., by pressing a button) once assembly of the device is completed. The device is arranged such that the syringe is driven forward during the needle advancement stage and subsequently the plunger is driven into the barrel during the dispensing stage for dispensing a liquid contained in the barrel. The device is arranged such that during operation of the device, a driving force is transmitted from the driving means to the plunger during the dispensing stage.

Description

INJECTION DEVICE

FIELD

The present invention relates to injection devices for the dispensing of liquids, and more particularly to automatic injection devices (so called "autoinjectors") including the assembly thereof.

BACKGROUND

Automatic injection devices are typically arranged such that when activated by a user, e.g. by pressing a button etc., an injection is automatically delivered. In order to automatically deliver an injection, such devices may be arranged to automatically advance the needle of a syringe for insertion into the body of a user, and depress the plunger to dispense liquid from the syringe barrel. The devices typically operate by having a number of movable components that interact with a driving means (e.g., one or more springs) and various mechanisms, so as to separate the stages of advancing the needle of the syringe for insertion, and driving the plunger into the barrel for dispensing a liquid contained in the barrel.

The needle of the syringe is typically protected by a cap, or “rigid needle shield”, which is typically larger in diameter than the needle. This causes difficulties in designing an auto-injector that permits insertion of the combined syringe and rigid needle shield during assembly, as well as removal of the rigid needle shield prior to activation of the automatic injection cycle.

Various auto-injectors have been proposed, but these are typically quite complex structures in view of the interrelated requirements discussed above. A known device is described in PCT application number PCT/GB2010/000078, which is owned by the Applicant and incorporated herein by reference in its entirety. This uses a plurality of rotating and translating components activated by the driving means that are configured to perform the automatic injection cycle. These components typically rotate around a common axis, and/or translate along the axis.

More recent devices (see, e.g., PCT application number PCT/EP2022/060710) have utilised abutments that translate radially (i.e. , transverse to the axis) to assist in the assembly of the auto- injector, and also separation of the various stages of the automatic injection cycle. These abutments have certain advantages, but they increase the complexity and can make it difficult to assemble the devices prior to use.

It is therefore desired to find a solution that can retain a similar degree of control whilst reducing the complexity of the device. It is also desired to provide a device that is easy to assemble and also ensures that the syringe is held safely throughout the automatic injection cycle. SUMMARY

The invention generally relates to an automatic injection device.

The device comprises a syringe having a needle, a barrel and a plunger, as well as driving means for driving the plunger into the barrel. The device may comprise a cap (e.g., rigid needle shield) configured to cover and protect the needle of the syringe prior to use.

The injection device is arranged to perform an automatic injection cycle in use comprising the stages of advancing the needle of the syringe for insertion (the "needle advancement stage"), and driving the plunger into the barrel for dispensing a liquid contained in the barrel (the "dispensing stage"). The automatic injection cycle may be activated (e.g., by pressing a button) once assembly of the device is completed.

The device is arranged such that the syringe is driven forward during the needle advancement stage and subsequently the plunger is driven into the barrel during the dispensing stage for dispensing a liquid contained in the barrel.

The device is arranged such that during operation of the device, a driving force is transmitted from the driving means to the plunger during the dispensing stage.

As used herein, the terms “forwards” and “rearwards” are intended to correspond to directions along the longitudinal axis of the device. References to “axial” or “radial” directions are similarly (unless stated otherwise) intended to be with reference to the longitudinal axis. This is typically (and preferably) also the axis of the syringe needle, and longitudinal axis of the syringe and its barrel.

In a first aspect of the invention, which may be claimed independently, the device further comprises a sleeve ("syringe sleeve" or “housing”) configured to capture the syringe and hold it in position (e.g., during assembly and/or the automatic injection cycle). The invention extends to a method of assembling the automatic injection device.

The syringe is insertable into the sleeve during assembly of the device, and the sleeve comprises members configured to flex outwards to allow passage of the needle and cap, and then flex back to catch and hold the syringe (e.g., during assembly and throughout at least the needle advancement stage of the automatic injection cycle).

This provides a safe and reliable mechanism for holding and securing the syringe during assembly and use, and especially for inserting the syringe during assembly, removal of the cap, and during the needle advancement stage of the automatic injection cycle.

The syringe may comprise a shoulder between the needle and the barrel, and the flexing members may be configured to catch onto the shoulder as they flex back. This advantageously makes use of the syringe geometry to provide a reliable and secure catch for the flexing members.

The flexing members may comprise one or more arms, each having a hook at the end thereof. The hooks may be configured to catch onto the syringe as the arms flex back. For example, the hooks may be configured to catch onto the shoulder of the syringe as the arms flex back.

The cap may be configured to urge the flexing members outwards as the syringe and cap are inserted into the sleeve. For example, during assembly as the syringe and cap are inserted into the sleeve, the members may ride up the outer surface of the cap and flex outwards. This advantageously takes into account the size of the cap, which is typically quite large, and can even comprise a diameter larger than the barrel of the syringe.

The sleeve may comprise an outer portion (referred to below as an outer syringe housing), as well as an inner portion (referred to below as an inner syringe housing) located concentrically within the outer portion and movable relative thereto, wherein the inner portion comprises the flexing members, which are configured to flex into and optionally through the outer portion in use. This provides a mechanism that allows easy control of the syringe movement (e.g., using the outer syringe housing), whilst providing a secure mechanism for holding the syringe in use (i.e. , the interaction between the inner and outer portions). The outer portion may comprise cavities or apertures configured to receive the flexing members of the inner portion.

Initially the inner portion may be located at a first, e.g. axial position relative to the outer portion, and the inner portion may be movable to a second, e.g. axial position relative to the outer portion. The inner portion may be configured to translate (i.e., without rotating relative to the outer portion) along the longitudinal axis of the device between the first and second positions, for example by moving along an axial track in the outer portion.

During assembly of the device, and while the inner portion remains in its first position, the syringe may be inserted into the inner portion, so that the flexing members ride over the cap, and then flex back to capture the syringe (e.g., the shoulder thereof). Once the syringe is captured, further pressure to insert the syringe causes the inner portion to move from its first position towards its second position. There is preferably no relative rotation between the inner portion and the outer portion as the inner portion translates (with the syringe) between its first and second positions. This avoids undesired twisting forces on the syringe during assembly.

The flexing members of the inner portion may be permitted to flex into and optionally through the outer portion as aforesaid (e.g., into the cavities or apertures) when the inner portion is in its first position. When the inner portion has moved to its second position, the flexing members may not be permitted to flex into or through the outer portion. For example, the flexing members may have moved out of alignment with the cavities or apertures by virtue of the inner portion moving (preferably translating) from its first position to its second position. These embodiments provide a simple, secure and reliable mechanism for controlling movement of the flexing members so that they catch and hold the syringe.

When the inner portion is in its second position the outer portion may be configured to prevent movement of the flexing members. The flexing members may for example be clamped between the syringe and the outer portion. The flexing members could be urged inwardly by the second portion towards the syringe. This means that they will reliably hold the syringe throughout its range of movement during assembly, and the automatic injection cycle.

During initial insertion of the syringe into the inner portion, the inner and outer portions may be configured to resist relative movement therebetween (e.g., by using detents between the outer and inner portions), such that the inner portion remains in its first position until the flexing members catch and hold the syringe.

As the syringe and cap are pushed into the inner portion during assembly, the cap may be configured to move past the flexing members whilst the inner portion remains in its first position. Once the cap has moved past the flexing members, a portion of the syringe may contact the inner portion to overcome the initial resistance (e.g., overcome the detents). Thereafter, further movement of the syringe pushes the inner portion to its second position (e.g., by translating it relative to the outer portion), so that the outer portion then captures the flexing members and prevents their flexing into and/or through the outer portion as aforesaid. As noted herein, it is preferred that the inner portion does not rotate relative to the outer portion during this assembly of the syringe into the sleeve.

The automatic injection device may further comprise an end, or device cap configured to cover and protect a dispensing end of the device, and the end cap may comprise means for removing the cap configured to cover and protect the needle of the syringe (i.e., the needle cap or rigid needle shield). For example, the end cap may comprise arms configured to extend into the device and catch the needle cap (i.e., the rigid needle shield) once the syringe and needle cap are fully inserted into the device (e.g., during assembly and/or once the inner portion is moved to its second position). After assembly but before activation of the automatic injection cycle, the end cap may be removed in order to remove the needle cap, such that the needle is exposed and ready for insertion into the user during the needle advancement stage.

The arms of the end cap may be configured to displace outwards (e.g., radially) to ride over the needle cap, and then clip onto a rear end thereof once they have done so. The end cap may be fitted before or after the needle has been inserted fully into the device during assembly, wherein the syringe is captured and held in position.

The removal of the needle cap or rigid needle shield is a particularly delicate step. As such the flexing members are configured to catch the syringe securely at this point (with e.g. the inner portion in its second position), so as to prevent damage to the syringe, for example via impaction forces on the syringe caused by removing the cap.

The method of assembly may comprise any of the assembly steps described above, and may be carried out by a machine or manually.

Accordingly, a method of assembling the automatic injection device may comprise providing a syringe and needle cap as described above, with the needle cap secured to the syringe and protecting the needle thereof.

The method may comprise inserting the syringe (with its cap) into the sleeve configured to capture the syringe and hold it in position, and such that during this insertion the members flex outwards allowing passage of the needle and cap, and then flex back to catch and hold the syringe as aforesaid.

The syringe may be inserted such that the flexing members ride up, over and past the outer surface of the cap, then flex back to catch onto and hold the syringe (e.g., at a shoulder thereof).

The syringe (with the cap) may be inserted into an inner portion of the sleeve as described above. The syringe is now held securely by the inner portion and cannot move relative thereto. At this point a portion of the syringe may contact the inner portion such that further movement of the syringe pushes the inner portion towards its second position.

The method may further comprise pushing the combined syringe and inner portion into the outer portion to its second position. In this movement the syringe may be securely held by the inner portion, in that the flexing members (e.g., hooks thereof) capture and prevent any movement of the syringe. For example the flexing members may be clamped between the outer portion and the syringe.

Either during this movement or after, the arms of the end cap may ride over the needle cap, and then clip onto a rear end thereof once they have done so. As such the combination of the syringe (with the cap), the sleeve configured to capture the syringe and hold it in position, and the end cap are assembled. The remaining parts of the device, for example any other sleeves or housing portions (e.g., an outer housing), may also be assembled by this point, meaning that the device is ready to use.

The method may include repeating the assembly steps for multiple automatic injection devices in a production line.

In a second aspect of the invention, which may be claimed independently or combined with the first aspect, the device further comprises a sleeve configured to advance forward to an extended position in which it covers/surrounds the needle. This advancement is designed to occur during the automatic injection cycle, and is not (for example) part of the assembly of the device.

If combined with the first aspect, the needle sleeve may be positioned concentrically between the syringe sleeve (e.g., the outer portion) and an outer housing. The end cap may fit over the outer housing, and extend into the device through the needle sleeve to clip onto the rear end of the needle cap as described above.

The needle sleeve may comprise one or more members configured to lock the needle sleeve in its extended position during the automatic injection cycle, at least subsequently to the dispensing stage (and perhaps before). This ensures that it remains in the extended position once the dose of liquid is dispensed from the barrel. Providing these locking members on the needle sleeve itself (as opposed to, e.g., a static portion of the device) simplifies the mechanism and aids in reliability.

The needle sleeve may be referred to as a needle shield, and is typically configured to be urged forwards by the action of a resilient member (e.g., spring). The resilient member may be biased between the needle sleeve and the outer housing.

Prior to activation of the automatic injection cycle the needle sleeve is held in place relative to a static part of the device (see e.g., the third aspect discussed below). After activation of the automatic injection cycle, the needle sleeve is released and permitted to advance forward to its extended position in which it covers/surrounds the needle.

Prior to activation of the automatic injection cycle the device may be pressed against the skin of the user, ready for the needle to advance into the skin. Once the automatic injection cycle is activated, the needle sleeve is released and will advance forwards towards the user's skin. Thereafter, as the device is pulled away (after the dispensing stage), the needle sleeve may continue to be urged and advance forward, until the locking members activate and prevent rearward movement. This means that the user and needle are protected throughout the automatic injection cycle, and afterwards.

The one or more locking members may be configured to flex to allow passage of a respective abutment as the needle sleeve advances forwards to its extended position. Each abutment may be configured to move past at least one respective flexing member as the needle sleeve advances to its extended position, such that the flexing members are then configured to flex back to lock the needle sleeve in its extended position by aligning with (and abutting) the abutment. The use of such flexing members on the needle sleeve provides a reliable mechanism for locking the needle sleeve, since their movement is governed by that of the needle sleeve, and not another part of the device.

The abutment(s) may be located on a static portion of the device, such as the outer housing, or another moving part (e.g., the outer portion or outer syringe housing described above).

The needle sleeve may comprise a track along which each abutment is configured to ride (e.g., translate) during advancement of the needle sleeve to its extended position. The abutment(s) and the needle sleeve may be configured such that there is no relative rotation therebetween throughout this advancement. This advantageously means that the device does not rely upon rotational movement to advance the needle sleeve.

Preferably, the needle sleeve may be configured to translate, that is held against rotation. This further reduces the reliance of the device on rotating elements to dispense the liquid from the syringe.

The flexing members may themselves provide at least part of the track (e.g., a pair of flexing members on opposed sides of a respective track), such that as the abutments move (e.g., translate) along the track, they cause the flexing member(s) to flex (e.g., as the abutments ride along them) to allow passage of the abutments along the track during advancement of the needle sleeve to its extended position, and then flex back once the abutment has moved past the flexing members and optionally reached the end of the track. This provides an optimised arrangement that securely guides the needle sleeve to its extended position whilst ensuring it is locked once completing this movement. This arrangement also does not require any relative rotation between the parts or radially moving members/elements, as with some conventional arrangements.

Where pairs of flexing members are provided, they may take the form of a pair of pincers. Two pairs of pincers could be diametrically opposed from each other, which balances the forces across the device. The pincers will flex away from each other to allow passage of a respective abutment.

The needle sleeve may comprise one or more pockets configured to receive a respective abutment once the needle sleeve has advanced to its extended position. Each pocket may be formed at least in part by the locking members (e.g., the ends thereof) and may be configured to hold a respective abutment in place (e.g., by preventing any movement relative to the needle sleeve), thereby locking the needle sleeve securely in its extended position.

Each pocket may be configured to receive a respective abutment, such that upon reaching the pocket (e.g., at the end of the track) the member(s) then flex(es) back to lock the needle sleeve in its extended position with the flexing member(s) aligning with (and abutting) the abutment as aforesaid.

The above arrangements are additionally advantageous in that they do not require any relative rotation between the parts or radially moving members/elements, as with some conventional arrangements.

In a third aspect of the invention, which may be claimed independently or combined with the first and/or second aspects, the device further comprises a sleeve configured to advance forward to an extended position in which it covers/surrounds the needle ("needle sleeve", wherein if combining with the second aspect this is the same needle sleeve described above), and the device further comprises a sleeve (or housing) configured to receive and hold the syringe during the automatic injection cycle, which sleeve is configured to move with the syringe at least during the needle advancement stage ("syringe sleeve", wherein if combining with the first aspect this is the same syringe sleeve described above). Prior to activation of the automatic injection cycle the needle sleeve is held in place relative to a static part of the device, and after activation of the automatic injection cycle, the syringe sleeve is configured to advance forwards and dislodge the needle sleeve from the static part of the device, such that the needle sleeve is then permitted to advance forward to its extended position in which it covers/surrounds the needle.

These combined features provide an effective and reliable mechanism for holding the needle sleeve in place prior to activation of the automatic injection cycle, and also ensuring the forward movement of the needle sleeve after activation of the automatic injection cycle.

The locking members of the second aspect described above could be combined with the features of this third aspect, to provide a complete, reliable mechanism for controlling the movement of the needle sleeve, all on the same sleeve and preferably without any relative rotation between the parts.

The syringe sleeve may be configured to advance forwards (e.g., translate without rotation) relative to the needle sleeve during the needle advancement stage of the automatic injection cycle, and preferably without any relative rotation between the syringe sleeve and the needle sleeve.

The syringe sleeve may comprise abutments that are configured to move (e.g., translate without rotation) along a track in the needle sleeve as the syringe sleeve advances forwards (e.g., translates without rotation) relative to the needle sleeve during the needle advancement stage. Once the abutments reach the end of the track, for example at the end of the needle advancement stage, they may be configured to dislodge the needle sleeve from the static part of the device as aforesaid. This then allows the needle sleeve to advance forwards to its extended position in which it covers/surrounds the needle.

The needle sleeve may be biased forwards by a resilient member (e.g., spring). The resilient member may be biased between the static part of the device and the needle sleeve, so as to urge the needle sleeve forwards relative to the static part of the device (and forward to its extended position in which it covers/surrounds the needle).

The needle sleeve may comprise flexing stop members configured to initially align with and abut the static part of the device to prevent forward movement thereof (prior to activation of the automatic injection cycle). The abutments on the syringe sleeve may be configured to dislodge the stop members by flexing them out of alignment with the static part of the device (e.g., as they move with the syringe sleeve), thereby permitting the needle sleeve to advance forward to its extended position in which it covers/surrounds the needle.

The stop members may comprise one or more pairs of members on opposed sides of a respective track, which are configured to move away from each other as the abutment dislodges them as aforesaid. For example, two pairs of pincers could be diametrically opposed to each other to balance the forces across the device. In a particularly advantageous design, a single needle sleeve could comprise both the locking members of the second aspect and the stop members of the third aspect. This significantly reduces the weight of the device as a whole, by combining the two functions into one sleeve.

For example, a single needle sleeve could include two diametrically opposed pairs of locking members (e.g., pincers as described above) and two diametrically opposed pairs of stop members, offset by about 90 degrees from the pairs of locking members. This provides both the dual-function needle sleeve, as well as the balancing of forces by using diametrically opposed members. To further optimise the needle sleeve it could be configured to only translate axially, without any rotation thereof.

These features of the invention are considered advantageous in their own right, and so in a fourth aspect of the invention, which may be claimed independently, the device further comprises a sleeve configured to advance forward from an initial position to an extended position in which it covers/surrounds the needle during or after completion of the needle advancement stage, wherein the needle sleeve comprises one or more first flexing members that are configured to initially prevent movement of the needle sleeve to its extended position, and wherein the needle sleeve comprises one or more second flexing members that are configured to lock the needle sleeve in its extended position at least subsequently to the dispensing stage to ensure that it remains in the extended position once the dose of liquid is dispensed from the barrel. Using first and second flexing members for these processes simplifies the operation of the device, and avoids the use of, for example, radially moving components such as collets or rotational movement of one or more of the sleeve elements.

The device may further comprise a sleeve configured to receive and hold the syringe during the automatic injection cycle, which sleeve is configured to move with the syringe at least during the needle advancement stage and hold it in position during the dispensing stage.

The first flexing members may be configured to initially align with and abut a first static portion of the device to prevent initial movement of the needle sleeve, and the syringe sleeve may comprise an abutment that moves with the syringe sleeve during the needle advancement stage and, as it moves, urges the flexing members out of alignment with the first static portion to allow the needle sleeve to advance forward to its extended position.

The second flexing members may be configured to ride along a second static portion of the device as the needle sleeve advances to its extended position, and then move past and flex back into alignment with the second static portion, thereby preventing rearward movement of the needle sleeve back towards its initial position.

As noted above, the first, second, third and fourth aspects may be claimed separately, or in any combination to provide an improved automatic injection device. The present invention provides an automatic injection device with reduced complexity. The device is easy to assemble and the syringe is held safely during assembly and then throughout the automatic injection cycle. By virtue of the present invention no rotating parts are required in the key stages of assembly, and throughout the needle advancement stage of the automatic injection cycle. The device of the present invention still provides beneficial features that may be provided in the prior art but with significantly more complexity (e.g., a captured/secure syringe, and controlled trigger or locking of the needle shield).

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will now be described, by way of example only, and with reference to the accompanying drawings in which:

Fig. 1 shows a cross-section through a device in accordance with an embodiment of the present invention;

Fig. 1 A shows an exploded view of the front portion of the device illustrated in Fig. 1 ;

Fig. 2 shows a similar view to Fig. 1 A, but in axial cross-section to expose certain features of the device;

Fig. 3 shows a side cross-sectional view of the device of Fig. 1 , prior to insertion of the syringe;

Fig. 4 shows a housing assembly for the syringe in isolation, and to illustrate the sliding relationship of inner and outer parts thereof;

Fig. 4A shows a cross-section of the device to illustrate the movement of certain features;

Fig. 5 shows a close-up of a dispensing end of the device in cross-section;

Fig. 5A shows a cross-section of the device to illustrate the movement of certain features;

Fig. 6 shows a sleeve for protecting a needle of the syringe used in the device in more detail, to show various features that control the axial movement of this part;

Fig. 6A shows a different perspective view of certain parts of the device to illustrate their interaction in more detail; and

Fig. 7 shows the structure of Fig. 6, but also including a front housing of the device and when certain parts are in their initial positions, that is prior to insertion of the syringe and the start of the automatic injection cycle.

DETAILED DESCRIPTION

Herewith will be described various embodiments of an automatic injection device as described above. Fig. 1 shows a cross-section of an automatic injection device 10, and Fig. 1A shows an exploded view of the front portion thereof, in accordance with an embodiment.

The device 10 includes a syringe 20, as well as a rigid needle shield 30, the combination of which corresponds to a well-known type of syringe used in auto injectors of this type. The rigid needle shield 30 is configured to protect and cover the needle 22 of the syringe 20 prior to loading the syringe 20 into the device 10.

The rigid needle shield 30 often has an outer diameter that is larger than the barrel of the syringe 20, as noted in the background above (although this is not essential).

The rigid needle shield 30 is illustrated as comprising two parts (see Fig. 2), although it will be appreciated that this could be provided in any suitable form, for example a single piece or multiple parts.

The device 10 includes driving means, in this case a spring 1 , sometimes referred to as a power or drive spring, which acts upon a drive cylinder 2 to depress the plunger of the syringe 20. An example of how to operate the device 10 to administer an injection is described in PCT application number PCT/GB2010/000078, which is owned by the Applicant and incorporated herein by reference in its entirety. As this functionality is not critical to the present invention it will not be described in detail herein.

Essentially, the drive spring 1 is configured to act upon the drive cylinder 2 arranged to selectively transmit a drive force to the plunger 26 of the syringe 20. The movement is guided using various mechanisms (e.g., cam surfaces) to ensure that the needle 22 is first advanced for insertion, after which the plunger 26 is depressed for dispensing a dose of liquid from the barrel. It is of course important that the needle 22 advancement and insertion is completed before the plunger 26 is depressed.

The device 10 is arranged to perform an automatic injection cycle in use comprising the stages of advancing the needle 22 of the syringe 20 for insertion (the "needle advancement stage"), and driving the plunger 26 into the barrel for dispensing a liquid contained in the barrel (the "dispensing stage"). The automatic injection cycle may be activated (e.g., by pressing a button) once assembly of the device 10 is completed.

The assembled device 10 is shown in Fig. 1 , prior to removal of the end cap (discussed below) and activation of the automatic injection cycle.

The device 10 is arranged such that the syringe 20 is driven forward during the needle advancement stage and subsequently the plunger 26 is driven into the barrel during the dispensing stage for dispensing a liquid contained in the barrel.

The device 10 is arranged such that during operation of the device 10, a driving force is transmitted from the driving means (e.g., drive spring 1) to the plunger 26 (via, e.g., the drive cylinder) during the dispensing stage. Referring back to Fig. 1A, the device 10 has a dispensing end 12, located at which is a front housing 50 that surrounds a syringe housing assembly comprised of an inner syringe housing 60 and an outer syringe housing 70. During assembly the syringe 20 and rigid needle shield 30 are loaded into the syringe housing assembly 60, 70 by inserting them into the inner syringe housing 60. Located between the syringe housing assembly 60, 70 and the front housing 50 is a needle sleeve 80, the function of which will become apparent from the description below.

The device 10 comprises an end cap 40 configured to cover and protect the dispensing end 12 of the device 10, including at least the forward-most portion of the front housing 50. As will be described below, the end cap 40 is removed from the device 10 prior to operation of the automatic injection cycle. As the end cap 40 is removed, it is configured to pull the rigid needle shield 30 away from the syringe 20, which exposes the syringe needle 22 ready for use (the mechanism for this is described below).

Fig. 2 shows a similar view to Fig. 1A, but in axial cross-section to expose certain features of the device 10.

The outer syringe housing 70 lies concentrically outside the inner syringe housing 60, which two parts are configured to slide axially relative to each other in a controlled manner, that is based on the action of the driving means. Preferably, the inner and outer syringe housings 60, 70 may be configured to slide purely axially, that is without any relative rotation between the two components. The inner syringe housing 60 comprises arms 62 that extend axially forwards of a main cylindrical body.

The ends of the arms 62 initially sit within apertures 72 of the outer syringe housing 70, as shown at least in Fig. 2. In this position the arms 62 are able to bend slightly outwards into the apertures. At the end of each arm 62 is a hook 63 that projects radially inwards.

Upon loading the syringe 20 and rigid needle shield 30 into the device 10, the rigid needle shield 30 moves past the arms 62 and contacts the hooks 63, urging them outwards. This causes the arms 62 themselves to bend outwards and allow passage of the rigid needle shield 30 past the arms 62.

Once the rigid needle shield 30 has progressed past the hooks 63, they are then configured to catch onto and retain the syringe 20 after it is pushed fully into the syringe housing assembly 60, 70. The arms 62 are then configured to move out of alignment with the apertures 72 so that they can no longer move radially outward. This will be described below, but principally the inner syringe housing 60 comprises a rear end 64 that is configured to interact with and contact a rear end 24 of the syringe 20 as it is pushed into the device 10 upon assembly (once the syringe 20 is pushed fully into the syringe housing assembly).

Located concentrically outside the outer syringe housing 70 at the dispensing end 12 is the needle sleeve 80, a front portion 82 of which is configured initially to extend past the outer syringe housing 70 and sit concentrically within the front housing 50. A spring 90 is biased between the needle sleeve 80 and the front housing 50, and is configured to urge the needle sleeve 80 in a forward direction. This can be achieved by biasing the spring 90 between respective radially extending members 83, 53 on a relatively forward part of the needle sleeve 80 and a relatively rearward part of the front housing 50, as shown in Fig. 2 (although other arrangements to achieve this are of course possible).

Fig. 3 shows a side cross-sectional view of the device 10 prior to insertion of the syringe 20 (i.e. , prior to assembly of the device 10).

In this position, the front housing 50 and the needle sleeve 80 interact to prevent forward movement of the needle sleeve 80 that would otherwise happen due to the action of the spring 90. This is achieved by the needle sleeve 80 comprising stop members 84 configured to bear axially against a portion of the front housing 50.

In the illustrated embodiment the stop members 84 bear against some of the radially extending members 53 of the front housing 50 (and on the opposite side of those members 53 to the spring 90). The radially extending members 53 of the front housing 50 may advantageously have the dual function of biasing the spring 90 on one side, and providing a stop surface for the stop members 84 of the needle sleeve 80 on the other. It is of course possible that more radially extending members 53 could be provided instead, some to bias the spring 90 and others to provide a stop surface for the stop members 84.

Fig. 4 shows the syringe housing assembly 60, 70 in isolation, and (in combination with at least Fig. 3) to illustrate the sliding relationship of the inner and outer parts thereof.

Fig. 4 shows the parts in their initial position, wherein the ends of the axially extending arms 62 of the inner syringe housing 60 are able to bend outward into respective apertures 72 of the outer syringe housing 70.

As the syringe 20 is inserted into the device 10, the rigid needle shield 30 will ride over the ends of the arms 62, pushing both the hooks 63 and the arms 62 radially outward into the apertures 72 as aforesaid. Once the syringe 20 has been pushed into the device 10 a given amount, an abutting portion thereof may contact a cooperating abutting portion of the inner syringe housing 60. For example, and as shown, the rear end 24 of the syringe 20 may contact the resilient rear end 64 of the inner syringe housing 60. Further movement of the syringe 20 into the device 10 thereby causes the inner syringe housing 60 to move axially with the syringe 20, and relative to the outer syringe housing 70.

The outer syringe housing is 70 is prevented from forward axial movement, for example by abutting stop members 41 of the end cap 40 (sees Figs. 4A and 5).

Referring back to Fig. 4, movement of the inner syringe housing 60 relative to the outer syringe housing 70 is guided, for example using a rail and track mechanism. Any suitable mechanism could be provided. In the preferred case of purely axial movement (i.e., without rotation), the mechanism would be configured to only permit axial movement between the inner syringe housing 60 and the outer syringe housing 70. A rail and track mechanism has been found to be particularly suitable for this, the track thereof being a purely linear/axial track.

Suitable detents 67 may be provided between the inner syringe housing 60 and outer syringe housing 70 configured to resist initial relative movement therebetween, for example whilst the syringe 20 and rigid needle shield 30 are inserted into the device 10 during assembly (and before the abutting portions of the syringe 20 and inner syringe housing 60 contact) . In the illustrated embodiment, the inner syringe housing 60 comprises radial protrusions 66 configured to slide within axially extending tracks 76 of the outer syringe housing 70 (although this could of course be the other way round).

Further axial movement of the syringe 20, and therefore the inner syringe housing 60 relative to the outer syringe housing 70 (e.g., overcoming the detents 67), causes the tips of the axially extending arms 62 of the inner syringe housing 60 to move beyond the apertures 72 of the outer syringe housing 70. This is shown in Fig. 4A, and means that the arms 62 are now prevented from moving radially outwards by the outer syringe housing 70.

By employing purely axial movement between the inner syringe housing 60 and the outer syringe housing 70, twisting forces on the syringe 20 are avoided or minimised. This reduces the chance of damaging the delicate components during assembly (particularly the syringe, which is typically made of glass).

The arms 62 now capture the syringe 20 and prevent its further movement forward into the device 10. This is ensured by the hooks 63 catching and holding a shoulder 23 of the syringe 20 (see Figs. 2, 3), which shoulder 23 sits adjacent a rear part of the rigid needle shield 30. Whilst the hooks 63 are configured to capture and hold onto the shoulder 23 of the syringe 20, they are, of course, not configured to capture the rigid needle shield 30 which can subsequently be removed from the device 10 using the end cap 40.

The present invention therefore solves the problem of how to assemble the (delicate) syringe 20 into the device 10 whilst subsequently holding the syringe 20 reliably during use, including when the needle 22 is advanced during the needle advancement stage, as well as when the plunger 26 is depressed during the dispensing stage (e.g., by the drive cylinder 2).

Once the syringe 20 is captured by its holding means (e.g., the hooks 63), it remains in this position held by the inner syringe housing 60 during use. As such, there is no impaction force on the syringe 20 as it moves with this holding means (i.e., the syringe housing 60, 70) during assembly and/or when the plunger 26 is depressed to dispense a liquid. This is particularly important for dispensing of viscous liquids from the syringe 20, which can cause high stresses on the various components (including, in particular, the delicate syringe 20). As noted above, preferred arrangements also reduce or eliminate twisting forces on the syringe 20, for example by only moving this axially through the device 10 during assembly (without rotation).

The present invention therefore avoids or reduces forces applied to the delicate syringe during assembly and use. The syringe is retained and held securely without the need, for example, for radially moving members (which have been proposed previously). The syringe is advantageously held under compression, which improves over conventional arrangements that hold the syringe under tension (stretching it) during assembly or use. As noted above, this is better for dispensing of all fluids, in particular viscous fluids.

The invention extends to a method of assembling the device, comprising the assembly steps defined herein. The assembly of the device includes inserting the syringe 20 as aforesaid, up until the inner syringe housing 60 has moved to its second position. At this point any additional housing elements may be connected to the device, such that it is ready to use and the automatic injection cycle may be activated.

Fig. 5 shows a close-up of the dispensing end 12 of the device 10 in crosssection, and with the arms 62 in their initial position.

In order to remove the rigid needle shield 30 prior to activation of the automatic injection cycle, the end cap 40 comprises arms 42 that extend into the central cavity of the device 10 (i.e., inside the needle sleeve 80 and syringe housing assembly). At the end of each arm 42 is a hook 43 configured to catch onto and remove the rigid needle shield 30. That is, the arms 42 are configured to extend far enough so that the hooks 43 can catch onto the rigid needle shield 30 when the syringe 20 and rigid needle shield 30 are pushed all the way into the device 10 upon assembly. The arms 42 are configured to displace radially outwards to allow the rigid needle shield 30 through, and then clip onto the rear end of the rigid needle shield 30 as shown in Fig. 5A.

As such, when the end cap 40 is subsequently removed (to allow the automatic injection cycle to begin), the hooks 43 catch the rigid needle shield 30, pulling it off the syringe 20 and removing it from the device 10.

As shown in Fig. 5A, at this point the arms 62 of the inner syringe housing 60 will have advanced forwards beyond the apertures 72 in the outer syringe housing 70 (see Fig. 4A), and as such the syringe 20 is safely and securely captured by the arms 62. Accordingly, as foreshadowed above the action of removing the end cap 40 and rigid needle shield 30 does not cause high stresses on the syringe 20 or needle 22 thereof. The axial position of the syringe 20 is unaffected, and it is prevented from further axial movement by the hooks 63 on the inner syringe housing 60.

Fig. 6 illustrates the needle sleeve 80 in more detail, to show various features that control the axial movement of this part. The needle sleeve 80 comprises the substantially cylindrical front portion 82, and a rear portion comprising diametrically opposed channels 86, which channels

86 comprise the stop members 84 adjacent their forward ends. At the forward end of each channel 86, and forward of the stop members 84, is a pocket 85 configured to receive a respective radially extending member 53a of the front housing 50. Initially, the stop members 84 are aligned with the radially extending members 53a (see Fig. 7), preventing forward movement of the needle sleeve 80.

The outer syringe housing 70 comprises diametrically opposed lugs 74. At their rearward ends, each channel 86 is substantially open to allow insertion of a respective one of the lugs 74 upon assembly. When assembling the device 10, the lugs 74 can be inserted into a respective channel 86, in which they may be initially held by detents 87 formed in the needle sleeve 80. The detents 87 may be formed by protrusions that extend into the channels 86 and cooperate with recesses in each lug 74. The detents 87, which are not essential, can prevent premature relative movement between the syringe housing 60, 70 and the needle sleeve 80 (in either direction), as the device 10 is being assembled and subsequently.

The lugs 74 are then configured to ride through each channel 86 as the outer syringe housing 70 moves as part of the automatic injection cycle (i.e., after the end cap 40 is removed from the device 10). That is, removal of the end cap 40 also removes the rigid needle shield 30 as discussed above, and exposes the needle 22 of the syringe 20 ready for the automatic injection cycle to begin. This cycle includes the stages of advancing the needle 22 of the syringe 20 for insertion, and driving the plunger 26 into the barrel 28 for dispensing a liquid contained in the barrel 28 (see Fig. 2).

As noted above an example of how to operate the device 10 to administer an injection is described in PCT application number PCT/GB2010/000078. Although this previous application describes a step of retracting the needle, this is not required in the illustrated embodiment since (as described herein) a needle sleeve/shield is advanced to cover the needle and protect it.

A driving force may therefore be applied to the outer syringe housing 70 using a mechanism as set out in the related application described above, for example a drive spring 1 and cylinder 2 as described above (or another suitable mechanism). This is part of the needle advancement stage of the automatic injection cycle, in which the needle 22 of the syringe 20 is advanced to protrude forwards from the front housing 50 so that it inserts into a user.

Upon action of the driving means, the lugs 74 are released from the detents

87 and move axially along the channels 86. As they progress through the channels 86, the lugs 74 move forwards towards the stop members 84. Throughout this movement the needle 22 will be advanced so that it can be inserted into the user.

Upon reaching the stop members 84, the lugs 74 are configured to shift them out of alignment with the radially extending members 53a of the front housing 50. As such, the needle sleeve 80 is no longer restrained from forward axial movement and the spring 90 urges the needle sleeve 80 forwards to cover and protect the needle 22 of the syringe 20. This may occur at the end of the needle advancement stage, so that as the injection is administered (and thereafter) the needle sleeve 80 is configured to press against the skin of a user, and then carry on moving forwards to its maximum extension to protect the needle 22 as the device 10 is pulled away from the user.

The device 10 is configured to ensure the needle sleeve 80 cannot move backwards once it reaches a given (e.g., maximum) extension. To achieve this the rear portion of the needle sleeve 80 comprises additional channels 186 that are diametrically opposed and offset 90 degrees from the channels 86 described above. The exact orientation of the channels 86, 186 is not critical, although having each pair of channels 86, 186 diametrically opposed and offset by 90 degrees (as illustrated) balances the forces across the device 10.

The additional channels 186 are provided to ensure that the needle sleeve 80 is prevented from rearward movement once it has moved a sufficient distance (e.g., a maximum distance) to cover and protect the needle 22.

Each additional channel 186 is configured to receive a radial extension 53b of the front housing 50 (see Fig. 7). In the initial configuration (prior to advancement of the outer syringe housing 70) the radial extensions 53b slot into the forward-most portion of the additional channels 186 (see Fig. 7). Once the automatic injection cycle has begun, and the needle sleeve 80 advances forwards (by action of the spring 90) the radial extensions 53b are configured to slide within the additional channels 186.

The needle sleeve 80 comprises arms 187 that extend rearward and form a narrowing rear portion of the additional channels 186. The arms 187 are prong-like, resilient members that are initially biased inwards into the additional channels 186 (i.e., relative to the longitudinal axis of the additional channels 186). As the radial extensions 53b slide within the additional channels 186 and reach the arms 187, they shift the arms 187 outwards as they move along them (i.e., away from the longitudinal axis of the additional channels 186).

As shown in Fig. 6A, once the extensions 53b slide past the arms 187, the arms 187 spring back into their initial position, at which point they block the radial extensions 53b and prevent their movement back down the additional channels 186. Thus, once the needle sleeve 80 is urged forward to its final position, it is prevented from rearward movement by the arms 187.

In order to hold the needle sleeve 80 in its final position as shown in Fig. 6A (i.e., without any axial movement), the radial extensions 53b of the front housing 50 slot into pockets 188 formed by the needle sleeve 80, and delimited in part by the rearward surfaces of the arms 187, as well as opposing protrusions 189. This captures the radial extensions 53b and prevents their movement in either axial direction. Fig. 7 shows the structure of Fig. 6, but also including the front housing 50 when the needle sleeve 80 and outer syringe housing 70 are in their initial positions.

As can be seen in Fig. 7, a first set of diametrically opposed radial extensions (indicated here as 53a) fit into the channels 86 and sit initially within the pockets 85. The stop members 84 align with these radial extensions 53a to prevent forward movement of the needle sleeve 80 as discussed above. Similarly, a second set of diametrically opposed radial extensions (indicated here as 53b) fit into the additional channels 186 and sit initially within the forward-most portion thereof. The second set of radial extensions 53b are then ready to slide along these channels and shift the arms 187 etc. as discussed above. As noted above, this particular configuration is an optimised arrangement to balance forces across the device 10, and it is not essential that specific numbers of radial extensions are provided, or that they are diametrically opposed as illustrated.

It will be appreciated that the stop members 84 and the arms 187 advantageously flex out of alignment with their respective abutments 53a, 53b on the front housing 50, to unlock and lock the needle sleeve 80. This is instead of using relative rotations between parts, or radially moving members as with the case for conventional arrangements. The only movement permitted by the device in use, therefore, is axial movement, which avoids rotating parts and the undesired bending/twisting forces associated therewith.

Although the present invention has been described with reference to various embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as set forth in the accompanying claims.

Claims

1. An automatic injection device comprising: a syringe having a needle, a barrel and a plunger; a cap (e.g., rigid needle shield) configured to cover and protect the needle of the syringe prior to use; and driving means for driving the plunger into the barrel, wherein the injection device is arranged to perform an automatic injection cycle in use comprising the stages of advancing the needle of the syringe for insertion, and driving the plunger into the barrel for dispensing a liquid contained in the barrel, wherein the device is arranged such that during operation of the device, a driving force is transmitted from the driving means to the plunger during the dispensing stage, wherein the device is arranged such that the syringe is driven forward during the needle advancement stage and the plunger is driven into the barrel during the dispensing stage for dispensing a liquid contained in the barrel, wherein the device further comprises a sleeve configured to capture the syringe and hold it in position during the automatic injection cycle, wherein the syringe is insertable into the sleeve during assembly of the device, and the sleeve comprises members configured to flex outwards to allow passage of the needle and cap, and then flex back to catch and hold the syringe during at least the needle advancement stage, wherein the sleeve comprises an outer portion, as well as an inner portion located concentrically within the outer portion and movable relative thereto, wherein the inner portion comprises the flexing members, which are configured to flex into and optionally through the outer portion in use, characterised in that the inner portion is configured to translate along the longitudinal axis of the device without rotating relative to the outer portion.

2. An automatic injection device as claimed in claim 1 , wherein the syringe comprises a shoulder between the needle and the barrel, and the flexing members are configured to catch onto the shoulder as they flex back.

3. An automatic injection device as claimed in claim 1 or 2, wherein the flexing members comprise one or more arms, each having a hook at the end thereof configured to catch onto the syringe as the arms flex back.

4. An automatic injection device as claimed in claim 2 and 3, wherein the hooks are configured to catch onto the shoulder of the syringe as the arms flex back.

5. An automatic injection device as claimed in any preceding claim, wherein the cap is configured to urge the flexing members outwards as the syringe and cap are inserted into the sleeve.

6. An automatic injection device as claimed in any preceding claim, wherein the flexing members are configured to flex through the outer portion in use.

7. An automatic injection device as claimed in any preceding claim, wherein the outer portion comprises cavities or apertures configured to receive the flexing members of the inner portion.

8. An automatic injection device as claimed in any preceding claim, wherein initially the inner portion is located at a first position relative to the outer portion, and the inner portion is axially movable to a second position relative to the outer portion without rotation, wherein in the first position the flexing members are permitted to flex into and optionally through the outer portion as aforesaid, and in the second position the flexing members are not permitted to flex into or through the outer portion.

9. An automatic injection device as claimed in claim 8, wherein in the second position the outer portion is positioned such that it prevents any movement of the flexing members.

10. An automatic injection device as claimed in claim 8 or 9, wherein the outer portion is movable relative to the inner portion during assembly of the device, wherein upon inserting the syringe into the inner portion during assembly the cap is configured to move past the flexing members whilst the inner portion remains in its first position, and then once the cap has moved past the flexing members further movement of the syringe is configured to push the inner portion axially to its second position without rotating relative to the outer portion, so that the outer portion captures the flexing members and prevents their flexing into and/or through the outer portion.

11. An automatic injection device as claimed in any preceding claim, further comprising an end cap configured to cover and protect a dispensing end of the device, wherein the end cap comprises means for removing the cap configured to cover and protect the needle of the syringe.

12. An automatic injection device as claimed in claim 11 when combined with any of claims 8-10, wherein the end cap comprises arms configured to extend into the device and catch the cap configured to cover and protect the needle once the inner portion has moved to its second position.

13. An automatic injection device as claimed in claim 12, wherein once the inner portion has moved to its second position the arms of the end cap are configured to displace outwards to ride over the needle cap, and then clip onto a rear end thereof once they have done so.

14. An automatic injection device comprising: a syringe having a needle, a barrel and a plunger; and driving means for driving the plunger into the barrel, wherein the injection device is arranged to perform an automatic injection cycle in use comprising the stages of advancing the needle of the syringe for insertion, and driving the plunger into the barrel for dispensing a liquid contained in the barrel, wherein the device is arranged such that during operation of the device, a driving force is transmitted from the driving means to the plunger during the dispensing stage, wherein the device is arranged such that the syringe is driven forward during the needle advancement stage and the plunger is driven into the barrel during the dispensing stage for dispensing a liquid contained in the barrel, wherein the device further comprises a sleeve configured to advance forward to an extended position in which it covers/surrounds the needle, wherein the needle sleeve comprises one or more members configured to lock the needle sleeve in its extended position at least subsequently to the dispensing stage to ensure that it remains in the extended position once the dose of liquid is dispensed from the barrel.

15. An automatic injection device as claimed in claim 14, wherein the one or more members configured to lock the needle sleeve in its extended position are configured to flex to allow passage of a respective abutment as the needle sleeve advances forwards to its extended position.

16. An automatic injection device as claimed in claim 15, wherein each abutment is configured to move past at least one respective flexing member as the needle sleeve advances to its extended position, such that the flexing members are then configured to flex back to lock the needle sleeve in its extended position by aligning with, and abutting the abutment.

17. An automatic injection device as claimed in claim 16, wherein the needle sleeve comprises a track along which each abutment is configured to ride during advancement of the needle sleeve to its extended position, wherein the flexing members provide at least part of the track, such that they flex to allow passage of the abutment along the track during advancement of the needle sleeve to its extended position, and then flex back once the abutment has moved past the flexing members and optionally reached the end of the track.

18. An automatic injection device as claimed in any of claims 14-17, wherein the needle sleeve comprises one or more pockets configured to receive a respective abutment once the needle sleeve has advanced to its extended position, wherein each pocket is formed at least in part by the locking members and is configured to hold a respective abutment in place, thereby locking the needle sleeve in its extended position.

19. An automatic injection device comprising: a syringe having a needle, a barrel and a plunger; and driving means for driving the plunger into the barrel, wherein the injection device is arranged to perform an automatic injection cycle in use comprising the stages of advancing the needle of the syringe for insertion, and driving the plunger into the barrel for dispensing a liquid contained in the barrel, wherein the device is arranged such that during operation of the device, a driving force is transmitted from the driving means to the plunger during the dispensing stage, wherein the device is arranged such that the syringe is driven forward during the needle advancement stage and the plunger is driven into the barrel during the dispensing stage for dispensing a liquid contained in the barrel, wherein the device further comprises a sleeve configured to advance forward to an extended position in which it covers/surrounds the needle, wherein the device further comprises a sleeve configured to receive and hold the syringe during the automatic injection cycle, which sleeve is configured to move with the syringe at least during the needle advancement stage, wherein prior to activation of the automatic injection cycle the needle sleeve is held in place relative to a static part of the device, wherein after activation of the automatic injection cycle, the syringe sleeve is configured to advance forwards and dislodge the needle sleeve from the static part of the device, such that the needle sleeve is then permitted to advance forward to its extended position in which it covers/surrounds the needle.

20. An automatic injection device as claimed in claim 19, wherein the syringe sleeve comprises abutments that are configured to move along a track in the needle sleeve, as the syringe sleeve advances forwards relative to the needle sleeve during the needle advancement stage of the automatic injection cycle, wherein the abutments are configured to dislodge the needle sleeve from the static part of the device as aforesaid.

21. An automatic injection device as claimed in claim 20, wherein the needle sleeve comprises flexing stop members configured to align with and abut the static part of the device to prevent forward movement thereof prior to activation of the automatic injection cycle, wherein the abutments on the syringe sleeve are configured to dislodge the stop members by flexing them out of alignment with the static part of the device, thereby permitting the needle sleeve to advance forward to its extended position in which it covers/surrounds the needle.

22. An automatic injection device as claimed in claim 19, 20 or 21, wherein the needle sleeve is biased forwards by a resilient member (e.g., spring).

23. An automatic injection device as claimed in claim 22, wherein the resilient member is biased between the static part of the device and the needle sleeve, so as to urge the needle sleeve forwards relative to the static part of the device.

24. An automatic injection device comprising: a syringe having a needle, a barrel and a plunger; and driving means for driving the plunger into the barrel, wherein the injection device is arranged to perform an automatic injection cycle in use comprising the stages of advancing the needle of the syringe for insertion, and driving the plunger into the barrel for dispensing a liquid contained in the barrel, wherein the device is arranged such that during operation of the device, a driving force is transmitted from the driving means to the plunger during the dispensing stage, wherein the device is arranged such that the syringe is driven forward during the needle advancement stage and the plunger is driven into the barrel during the dispensing stage for dispensing a liquid contained in the barrel, wherein the device further comprises a sleeve configured to advance forward from an initial position to an extended position in which it covers/surrounds the needle during or after completion of the needle advancement stage, wherein the needle sleeve comprises one or more first flexing members that are configured to initially prevent movement of the needle sleeve to its extended position, wherein the needle sleeve comprises one or more second flexing members that are configured to lock the needle sleeve in its extended position at least subsequently to the dispensing stage to ensure that it remains in the extended position once the dose of liquid is dispensed from the barrel.

25. An automatic injection device as claimed in claim 24, wherein: the device further comprises a sleeve configured to receive and hold the syringe during the automatic injection cycle, which sleeve is configured to move with the syringe at least during the needle advancement stage and hold it in position during the dispensing stage; the first flexing members are configured to initially align with and abut a first static portion of the device to prevent initial movement of the needle sleeve, and the syringe sleeve comprises an abutment that moves with the syringe sleeve during the needle advancement stage and, as it moves, urges the flexing members out of alignment with the first static portion to allow the needle sleeve to advance forward to its extended position; and the second flexing members are configured to ride along a second static portion of the device as the needle sleeve advances to its extended position, and then move past and flex back into alignment with the second static portion, thereby preventing rearward movement of the needle sleeve back towards its initial position.